Minimisation of damage to wool

1. Minimisation of damage to wool • The advantages of high temperature dyeing above 1100C are • Fast deep shades • Shorter leveling time • Better levelling • Less staining of wool • Disadvantages • Wool degradation –reduction in strength, elongation, abrasion resistance, yellowing

2. Therefore, to protect the wool component during high temperature dyeing, • Most common agent HCHO (5% owf) allows dyeing at • 1050C for 4 hrs • 1100C for 3 hrs • 1150C for2 hrs • 1200C for 1 hr • pH: 3.5-4.5

3. Recommended dyeing times • 1000C for 120-150 min with carrier, no formaldehyde • 1060C ,90 –120 min with carrier and without formaldahyde • 110 -1150C, 60 –90 min, reduced amount of carrier, formaldehyde necessary • 1200C, 20-30 min (not >40 min), carrier optional, formaldehyde necessary • High temperature dyeing is recommended for deep shades –yellowing is not so critical

4. Precautions for formaldehyde use • Shades of some dyes are affected -careful dye selection • HCHO vapours are potentially hazardous -restricted use by health and safety considerations • Therefore, agents which will release HCHO during dyeing (in-situ release) are preferred. E.g DMEU -HCHO release above 00C

5. Dyeing methods: • One bath dyeing method with disperse and acid or metal complex dyes • Dye selection: • Disperse dye –low energy ->minimum staining of wool –easily removed by after wash • Acid or metal complex –not so critical

6. General dyeing recipe • X% disperse dye • Y% acid/metal complex dye • Z% carrier • 1 –2% dispersing agent • 5 -10% glauber’s salt • pH :4.5 –5.5 with acetic acid

7. Dyeing procedure • Set bath with auxuliaries • Preheat 10 –20 min at 50 -700C • Add disperse and dissolved acid dye • Treat for 10 min • Raise temperature to boil or 103-1060C 30-45 min • Dye for 1½-2hrs depending on depth of shade • Cool, cold and hot rinse –shading 80 -1000C

8. One-bath dyeing • Improve dye exhaustion • Minimise wool staining • Wool protecting agent is necessary • Recipe: • X% disperse dye • Y% acid / metal complex dye • 3-5% HCHO (30%) • 1-2% dispersing agent , pH : 5 -6 with HAC’

9. Pretreat with auxiliary at 50-600C • Add disperse and acid dyes • Treat for 10 min • Raise temperature to 1100C/1200C in 45 min • Dye for 30 –60 min

10. After treatment • Staining of wool with disperse dyes cannot be avoided even if the process is carried out with most siutable dyes under the most favourable conditions • Disperse staining on wool –poor fastness –must be removed completely • One-bath method –reduction clear is not possible • After wash: 1-2 gpl non-ionic detergent, pH 5-6 with HAC’, 20-30 min at 600C, good rinse • With deep shades, repeat the above process

11. Two bath process • Used for deep shades -particularly navy and black • Dye polyester component with • X % disperse dye • Y% carrier • 1 –2% dispersing agent • pH 5-6 with HAC’ • Maximum temperature :103 -1060C or boil • Cold rinse

12. Reduction clearing: • 3 gpl hydrose • 0.5- 1 ml/l ammonia(25%) • 0.5-1 gpl non-ionic emulsifying agent • For 30 min at 45 -500C • Good rinse, acidify with HAC’ • Dyeing of wool component

13. Thermosol dyeing • Not common • Can be used for coloration of PET component only • Wool component is dyed seperately (detail sin page 256-257) • Dry heat treatment: • 190 -2000C for 45 –60 secs • Not harmful to wool except slight yellowing • Less wool staining

14. Correction of faulty dyeings • Faulty shades can be levelled or partially stripped with • X gpl carrier • 2-4% levelling agent for wool • 1 –2% emulsifying agent • pH 5-6% with HAC’ • Treatment at boil for 1 –2 hrs or 103 -1060C for 1 –1 ½ hrs If only shade on wool is to be corrected, carrier is not necessary